This invention relates to packing elements of the type that are often called “random” or “dumped” packings. Such packings are used to fill towers units in which mass or heat transfer processes occur. A particularly important application is the use of such ceramic elements in heat recovery operations where it is necessary to provide maximum effective contact with hot fluids passing through the reactor. Another key factor in maximizing efficiency is the maintenance of as low a pressure difference between top and bottom of the tower as possible. To ensure this the packing elements should present the minimum resistance to flow. This is promoted by very open structures but open structure alone is of limited use if the elements in the tower nest together such that parts of one packing element penetrate within the space of a second element. It is therefore important that the design of the elements minimize the tendency of the elements to nest together.
The present invention relates particularly to ceramic packing elements that are produced by an extrusion or a dry-pressing process and hence have an essentially uniform cross-section along one axial direction which provides an axis of symmetry for the element. Several such shapes have been described in the art ranging from the very simple to the complex. All are based on an essentially cylindrical shape and differ basically in the internal structure within the cylindrical shape. The simplest structure is a basic cylinder with no internal structure at all. This type of structure is often called a Raschig ring and has been known for many years. At the other end of the complexity scale are the structures described in U.S. Pat. No. Design 445,029 and U.S. Pat. No. 6,007,915. Between the extremes there are simple wagon-wheel shapes such as are described in U.S. Pat. Nos. 3,907,710 and 4,510,263.
It has now discovered that the dimensions of these shapes are critical to achieving optimum performance and the range of dimensions for such optimum performance has not been taught in the prior art. U.S. Pat. No. 4,510,263 teaches L:D ratios of 0.5 to 5 but indicates that preferred ratios are from 0.5 to 2. In U.S. Pat. No. 3,907,710 there is no teaching on the aspect ratio but the Examples use elements with the ratio of 1. U.S. Pat. No. 4,337,178 which teaches cylindrical ceramic elements as catalyst supports, also does not teach specific preferred aspect ratios but utilizes in the Examples elements with aspect ratios of 2.11.